Apparatus for the concentrating of minerals by means of froth flotation



Sept. 22, 1953 R WUNSC APPARATUS FOR THE CONCENTRATING OF MINERALS BYMEANS OF FROTH FLOTATION Filed July 20, 1949 IVNTOR.

Patented Sept. 22, 1953 APPARATUS FOR THE CONCENTRATING; F. MINERALS. nYMEANS OF FRoTn morp Rudolf Wunsch, Milan, Italy Application J uly20,1949, Serial-No, 105,8,i8v

In ItalyvJuly 21, 19%18 8' Claims. (01. 209-169) It is the. object of.the present invention to Provide. such improvements. in oi' relating topar tus a car ou re c e n r t on b thefroth flotation process, as mayresult in ape paratus of anew type or be'applied with an.- paratus qfother types already existing or of new types that might be developed andproposed. Flotation machines operating by mechanical agitation arel nownwherein aeration of the pulp is proyidedby a rotating impeller in anagitatin compartment divided by a vertical. wall from the rot emana in mar t a wall having in its upper portion a port through which the pulpenters into a frothing chamber having a hopper shapa the so-calledspitzlrasten. At the bottom of this spitzkasten there is a pipe. forreturning the pulp to the rotor on impeller in the. a in com a tmen Itwas found that these impellers lprovide maximum, aeration of the pulp ifthey carry radial blades revolvingunder. and close to a flange; however,this type of impeller requires much power for maintaining sufficientcirculation of the pulp between agitating compartment and spitzlzasten.On the other hand, if the impeller is provided with curved bladeslikethose of. a centrifugal pump, power requirements diminish, butaeration also diminishes considerably. The attempt was made toeliminate. this moonvenience by providing a double rotor equipped withboth curved blades and radial blades, the pulp entering into the doublerotor from. top and passing partly through the radial blades and partly"through the curved blades, so that suflicient aeration and circulationis attained.

The present invention provides for two separate rotors in the agitatingcompartment; a lower rotor at the bottom of the agitating compartment,"shaped like the rotor of a centrifugal pump; and upperrotorcarryingradial blades. The connection b'etweenthese two rotors is such that thelower'rotor forces the whole pulp, both the pulp fed from the preceding.cell and the pulp circulating inside the compartments to pass throughthe upper rotor, in order to attain perfeet aeration. It is therefore aspecific object of thepresent invention to provide a froth flotatapparatus in whieh the agitating comparttans thespitskasten are adjacentone an- 1 the thefagitating compartment is d i d, "to. up er. ge n nd agt n 'f and a are be a d, a itatii i'e r i it l v ah rizl etina tiiiee haI A g therein constituting the lower compartments and in which in eachcompartnient impeller means are arranged, in the lower compartment saidmeans constituting a. pump means including a substantially enclosedrotor and in the upper compartment an impeller constituting a combinedaerating andagitating impeller and in which means are providedforleading the pulp from the spitsliasten to and feeding the samecentrallyv of the rotor in the lower omp r m nt an a c s n rw ds he m en he u er ompa tmen tends up wardly therewithin, terminates atleastadjacent the pulp. ev nd s n, wmml ieet h ith the a t s t ae at thepulhe e a.- m i is Such a with q nirelleb e in between theupper compartmentand the spits} kasten open and. pulp fed, to the lower coinpart: mentthe circulation Of, pulp is efiected and all pulp entering the lower,compartment must pass through the singlet opening inthe horizontalpartition into the sphere of action of the inipeller in the. uppercompartment and which latter impeller is operative. to draw air into thecasing to mix the same with the. pulp.

It is a further and more specific. object to incorporate stationarydeflector means in the lower pumping compartment that is positionedsubjacent the aperture. in the horiz ontalparti tion and has a surfacewhich in vertical. cross.- section and in combination with theundersurface of the. horizontal partition definesa Venturi type throatso as to accelerate pulp flow through the single opening in thehorizontal partitien into the sphere of action of the upper impeller.

It is an additional specific object to incorporatea downwardly open bellmouth flange and to mount the rotor of the pump in position to rotateclosely adjacent this flange and provide means for feeding new pulp andmeans for leading pulp from the spitskasten centrally of this bell mouthflange so that all pulp is fed to the rotor of the pump centrallythereof.

Further and more specific objects will be apparent in the following,detailed description.

An embodiment of the present invention is i1.- lustrated in theaccompanying drawings, in which:

Figure 1 is a longitudinal sectional view.- thereof with some partsshown in elevation;

Figure 2 is a top plan view oi; the rotor in the pumping compartment andillustrating the vature ofthe blades thereof; and

Figure 3 is a vertical sectional view through the. stationary deflectorand the bell-mouth flange depending therefrom and located pumpingcompartment and taken at right angles to the illustration thereof inFigure 1 and looking toward the left in Figure 1.

In the arrangement illustrated the fresh pulp flowing from a ball millor pulp flowing from a preceding cell passes through pipe l and into thediflusor 2 into which circulating pulp returned from the spitzkasten Zllalso enters through pipe I8. Under and closely adjacent the bell mouthflange of the diffusor there is arranged the bottom rotor 3 which hascurved blades and is driven by the shaft 4. As shown in the drawing thisrotor 3 is substantially enclosed since the horizontal disc supportingthe same is imperforate and the respective pulp conduits constitutingthe pipes l and i8 feed the pulp centrally within the bell mouth flangeso that the pulp is fed centrally of this rotor. Thus the cooperation ofthe rotor with the flange in the manner of pulp feed defines acentrifugal pump. The pulp pumped through rotor 3 passes through thecentral circular port or aperture in the horizontal partition 6.Subjacent this aperture there is arranged the deflector bafile i whichhas a spherical upper surface and therefore, the whole of the pulp mustpass at considerable speed through said central circular port to flowcentrally of and beneath the lower part of a double rotor provided withupper and lower radial blades 9 and 8 respectively and driven by theshaft 10. This double rotor revolves within a cylinder l2 having anopening in the wall thereof directed toward the grid l controlling pulpflow into the spitzkasten. Since the pulp raised by the bottom rotorenters the sphere of action of lower part of the double rotor atconsiderable speed owing to the shape and position of the deflectorbafiie 1, this lower part of the rotor, having the radial blades 3,consumes little power because its task is not to accelerate I the pulpbut only to aerate it and direct its flow into the spitzkasten.

As a matter of fact, experiments on an industrial scale have evidencedthat a considerable reduced speed of operation of the radial-bladedrotor is possible while maintaining active aeration of the pulp. Theupper part of the double rotor also carries radial blades 9 turningunder a flange formed by the conical vessel I i and this part serves toaerate the overflow, which is adjustable at will by adjusting theposition of the gate l3 through which the pulp is discharged to thsubsequent cell. The level of the pulp in the spitzkasten 29 can beadjusted at will by raising or lowering the grid 15 by means of the handwheel It. The grid I? in the spitzkasten serves to calm down the pulpimpelled by the double rotor. In order to ensure rapid progress of thefroth toward the discharge scraper 22, a movable apron 2| is so arrangedas not to restrict the frothing surface.

It is therefore clear that this invention provides a froth flotationapparatus comprising tank means which includes a vertical partition anda horizontal partition 6 extending from on side of and intermediate theends of the vertical partition. These two partitions divide the tankmeans into three compartments comprising an aerating and agitatingcompartment above the horizontal partition, a pumping and agitatingcompartment beneath this horizontal partition and a spitzkasten on theopposite side of the vertical partition. The horizontal partition isprovided with a single central opening therein affording communicationbetween the pumping and agitating compartment and the aerating andagitating compartment. The vertical partition has an opening thereinabove the horizontal partition which is controllable and which providesa communication between the upper aerating and agitating compartment andthe spitskasten. A pump means is provided in the pumping compartment andincludes a substantially enclosed rotor and in addition the conduits land I8 are provided which feed new pulp and pulp contained in thespitskasten centrally of the bell mouth flange beneath which the rotor 3rot/ates so that all pulp is introduced centrally of this rotor so thatwhen the same is operating it draws the pulp into the center thereof toagitate the same and force the pulp to flow through the single centralopening in the horizontal partition. When the pump is in operationtherefore, a pulp circuit is afforded between the three compartments.Within the upper aerating and agitating compartment there is provided acylindrical casing of greater diameter than and surrounding the singleopening in the horizontal partition. This casing extends upwardly fromth horizontal partition and terminates at least adjacent the pulp levelthat is maintained in the upper aerating and agitating compartment inaccordance with the adjustment of the gate I3. The casing is open to theair, that is to aerate the pulp and in the position of adjustment shownthis casing terminates slightly beneath the pulp level in the uppercompartment so that pulp cascades into the casing in a thin veil. Thiscasing l2 is provided with an opening in the wall thereof that faces theopening providing communication with the spitskasten. An aerating andagitating impeller is mounted within the casing for rotation on avertical axis. This impeller includes a horizontal disc having upper andlower sets of radial blades with the lower radial blades disposedclosely adjacent the horizontal partition. The

' operation of this impeller sets up a suction action as regards thecasing so as to suck air into the casing and beat the same into thepulp. The lower .blades are impinged upon by the pulp forced by the pumpout of the lower compartment which action enables the operation of theupper impeller at reduced power and which upper impeller will acceleratethe agitation of pulp initially agitated in the pumping compartment andthoroughly mix air with all the pulp that flows through the centralaperture in the horizontal partition.

As shown in the drawings the deflector means I is positioned coaxiallyof and subjacent the single opening in the horizontal partition. Thisdeflector constitutes a body having a spherical upper surface so as toprovide a channel of decreasing or reducing size or width between theouter limits of the deflector and the opening. In other words anyvertical cross-section taken through deflector I and the horizontalpartition defines a space between the partition and the upper surface ofthe deflector that narrows in width toward the central opening toprovide a Venturi type throat to accelerate pulp flow through saidsingle opening, as shown in Figures 1 and 3.

The arrangement therefore provides froth flotation apparatus in whichall new pulp must be subjected to the action of the pumping andagitating rotor and the upper aerating and agitating impeller andadditionally any pulp that has passed through these two mechanisms andflow into the spitskasten positively recirculated at least once throughboth of these impeller means before it n ove f ow thr gh the gate I3 tothe next cell. w

As-isclearfrom the showing-inFigures-l' and 3', the'means for leadingpulp from the spitskasten to and feeding the same centrally of the rotorincludes the conduit 18' iii-communication with the spitskasten beneaththe horizontabpartition and extending within the pumping compartment.The stationary deflector body 7 mounted' beneath the single centralopening in the horizontal partition has an aperture therethroughincommunication with the conduit Hi. This aperture-terminates in adownwardly directed opening above the rotor. The raw pulp inlet conduiti also extends within the pumping compartment. The deflector body hasanother aperture therethrough that terminates in a downwardly directedopening above th rotor. This aperture: communh cates with conduit I. Anannular depend gbell" mouth flange is embodied with the body for partlydelimiting and surrounding both the-said openings. The rotor'rotatesclosely adjacent this flange so that'the pulp feedscentrallythereoffrom'both said openings.

The two rotors may be driven by separate shafts or by a single shaft.Ofcourse; the inven tion may be embodied'in a manner different from thatillustrated, without departing from. the scope'ofthe invention asdefined'in the appended claims.

Having now particularly described-andascermined the nature of my saidinvention and: in what manner. the same is to be performed; Ideclarethat'what I claim is:

1. In a froth flotationapparatus means defining an agitation compartmentand a spitslrasten both adapted to contain pulp, a vertical:wallseparating the same, ahorizcntal partition dividing the agitatingcompartment into an upper aerat ing and agitating compartment and. alower pumping and agitating compartmenheaid horizontal partition havingonly a single opening therein, said wall having an opening therethroughabove the horizontal partition andproviding" communication between: saidupper compartment and said spitskasten, pump means within the pumpingcompartment including a substantially enclosed. rotor, means for leadingpulp from the spitslrasten to and feeding the same centrally oi therotor, a cylindrical asing surrounding said opening in the horizontalpartition and extending upwardly within said upper compartment andterminating at least adjacent the pulp level therein, said casing beingin communication with the air that is to aerate the pulp and having anopening therein adiacent the horizontal partition, a combined aeratingand agitating impeller within the casing and rotatable therein. at thelevel of said last mentioned opening, and operative to draw into thecasing to mix same at least with the pulp forced through said singleopening by said pump rotor.

2. Froth flotation apparatus comprising tank means including a verticalpartition and a horizontal partition extending from one side of andintermediate the ends of the vertical partition, said two partitionsdividing the tank means into three compartments comprising an aeratingand agitating compartment above the horizontal partition, a pumping andagitating compartment heneath said horizontal partition, and aspitskasten on the opposite side of the vertical partition, saidhorizontal partition having a single central opening therein providingcommunication between the pumping and agitating compartment and theaerating and agitating compartment, said verthe pumping. and agitatingcompartment and; the

tical' partition-- having; an opening therein: above the horizontalpartition to provid communication between the aerating andagitatingcompartment and thespitskasten, apump means in the pumping compartmentincludinga substantially enclosedrotor, means for feeding pulp into thepumping compartment including means for introducing pulp to said rotorcentrally thereof, means for" leading pulp from said spitskasten to themeansior introducing-pulp centrally of the rotor so that operation oftherotor draws pulp into thecenterthereof'toagitate the sameand 'lorcepulp through the single central opening in the'horizont-al partitionfrom whence it passes through saidaerating and agitating compartment andlows into-said spitskasten for-recirculation and frothseparation, acylindrical casing surrounding the single central opening in thehorizontal partition, extending upwardly thereof and terminating atleast adjacent thepulplevel in theaerating and agitating compartment,said casing being open to the air, and'said casing further having-anopening above the horizontal partition and directed toward the openingproviding communication with the spitskasten, an

tion, a pumping and agitating compartment beneath said horizontalpartition, andaspitskasten on the opposideside of the verticalpartition, said horizontal partition-having a single central openingtherein providing. communication between aerating. and agitatingcompartment, said verticalpartition having an opening therein above thehorizontal partition to providecommunication:betweenthe aerating; andagitating com artment and the spitskasten, a pumpmeansin-the pumping:compartment including a substantially enclosed rotor; means for feedingpulp into the pumping compartment, including: means for introducing pulpto; said rotor centrally thereof, means for leading; pulp from saidspitsliasten to the means for introduc ng pu pcentrally Of the rotor sothat operation of the rotor draws pulp into the center thereof toagitate the same and force pulp through the single central opening inthe horizontal partition from whence it passes through said aerating andagitating compartment and flows into said spitskasten for recirculationand froth separation, a cylindrical casing surrounding the singlecentral opening in the horizontal partition extending upwardly thereofand terminating at least adjacent the pulp level in the areating andagitating compartment, said casing being open to the air, and saidcasing further having an opening above the horizontal partition anddirected toward the opening providing communication with thespitskasten, an aerating and agitating impeller mounted within saidcasing, and including a horizontal disc having upper and lower sets ofradial blades, and

with the lower radial blades disposed closely adjacent the horizontalpartition, said agitating impeller drawing air into the casing to mixwith the pulp and further accelerating the agitation of the pulpinitially agitated in the pumping compartment so as to thoroughly mixair with all pulp flowing through the single central opening in thehorizontal partition.

4. Froth flotation apparatus as defined in and by claim 3 and includinga stationary deflector positioned coaxially of and subjacent the singlecentral opening in the horizontal partition, said deflector constitutinga body having an upper surface defining in vertical cross-section and incooperation with horizontal partition a conduit of reducing size withthe narrowest size being adjacent the said single central opening so asto provide a Venturi type throat through which all pulp contained in thepumping and agitating compartment must pass and said throat acceleratingpulp flow to the upper aerating and agitating compartment.

5. Froth flotation apparatus as defined in and by claim 3 in which thecylindrical casing surrounding the single central opening in the horithetop to the bottom of the casing and terminating in spaced relation tothe upper surface of ,said horizontal partition and defining a central.axial opening in the cylindrical casing, said casing terminating atleast slightly beneath the pulp level in the aerating and agitatingcompartments so that pulp cascades over the same and through the saidcentral axial opening, horizontally disposed flange portions extendingbetween the lower terminal end of the conical surface and the innersurface of said casing, and the upper radial blades of said aerating andagitating impeller being rotatable immediately subjacent the saidhorizontal flange portions so that when said agitating and aeratingimpeller is rotating air is sucked through the casing together with thepulp cascading thereinto and which pulp and air are thoroughly mixedwith the pulp flowing from the lower pumping and agitating compartmentthrough the said single opening in the horizontal partition.

6. A froth flotation apparatus as defined in and by claim 1 in which themeans for leading pulp from the spitskasten to and feeding the samecentrally of the rotor includes a conduit in communication with thespitskasten beneath said horizontal partition and extending within thepumping-compartment, a stationary deflector body mounted within thepumping compartment subjacent the single central opening and having anaperture therethrough with which said conduit communicates, saidaperture terminating in a downwardly directed opening, a dependingannular bell mouth flange embodied with said body and surrounding saidlast mentioned opening, and said pump rotor being rotatable closelysubjacent said bell-mouth flange and receiving pulp centrally thereoffrom said downwardly directed opening.

7. A froth flotation apparatus as defined in and by claim 6, and furtherincluding a raw pulp inlet conduit extending within said pumpingcompartment and terminating therewithin, said stationary body havinganother aperture therethrough terminating in a downwardly directedopening, said last mentioned aperture being in communication with saidraw pulp inlet conduit at one end and through said downwardly directedopening with said bell-mouth flange at the other.

8. A froth flotation apparatus as defined in and by claim 7, and inwhich said stationary body is mounted coaxially beneath said singleopening in the horizontal partition and has a spherical upper surface,the axis of which is coaxial with said opening so that the said uppersurface in cooperation with the undersurface of said horizontalpartition defines a pulp conduit of reducing width with the narrowestwidth adjacent said single opening in the horizontal partition therebyaccelerating pulp flow into and through said single opening in thehorizontal partition.

RUDOLF WUNSCH.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 1,277,750 Pearce Sept. 3, 1918 1,457,077 Janney May 29, 19231,463,405 Ruth July 31, 1923 2,148,446 Drake Feb. 28, 1939 2,189,779Daman Feb. 13, 1940 2,240,671 Shorlino May 6, 1941 2,246,560 Weinig June24, 1941 2,410,429 Daman Nov. 5, 1946 2,433,592 Booth Dec. 30, 1947OTHER REFERENCES Taggart: Handbook of Ore Dressing, John Wiley and Sons,Inc., New York 1927, pages 802, 803.

Taggart: Handbook of Mineral Dressing, John Wiley and Sons, Inc., NewYork 1945. Section 12, pages 12-77 and 12-78.

